There is an ongoing demand in the aerospace industry for low cost electromagnetic coils suitable for usage in coiled-wire devices, such as actuators (e.g., solenoids) and sensors (e.g., linear variable differential transformers), capable of providing prolonged and reliable operation in high temperature environments and, specifically, while subjected to temperatures in excess of 260° C. It is known that low cost electromagnetic coils can be produced utilizing aluminum wire, which is commercially available at minimal cost, which provides excellent conductive properties, and which can be anodized to form an insulative alumina shell over the wire's outer surface. However, the outer alumina shell of anodized aluminum wire is relatively thin and can easily abrade due to contact between neighboring coils during winding. As a result, bare anodized aluminum wire is prone to shorting during the coiling process. Coil-to-coil abrasion can be greatly reduced or eliminated by utilizing anodized aluminum wires having insulative organic-based (e.g., polyimide) coatings to form the electromagnetic coil; however, organic materials rapidly decompose, become brittle, and ultimately fail when subjected to temperatures exceeding approximately 260° C.
A limited number of ceramic insulated wires are commercially available, which can provide continuous operation at temperatures exceeding 260° C.; however, such wires tend to be prohibitively costly for most applications and may contain an undesirably high amount of lead. High temperature wires are also available that employ cores fabricated from non-aluminum metals, such as silver, nickel, and copper. However, wires having non-aluminum cores tend to be considerably more costly than aluminum wire and may be incapable of forming an insulative oxide shell. In addition, wires formed from nickel tend to be less conductive than is aluminum wire and, consequently, add undesired bulk and weight to an electromagnetic coil assembly utilized within avionic applications. Finally, while insulated wires having cores fabricated from a first metal (e.g., copper) and claddings formed from a second meal (e.g., nickel) are also known, such wires are relatively costly, which tend to become less conductive over time due to diffusion of the cladding material into the wire's core, and may exhibit alloying-induced resistance creeping when exposed to elevated temperatures for longer periods of time. Additionally, wires employing metal-clad conductors still require electrically-insulative coatings of the type described above.
Considering the above, there exists an ongoing need to provide embodiments of a electromagnetic coil assembly suitable for usage within high temperature coiled-wire devices (e.g., solenoids, linear variable differential transformers, and three wire position sensors, to list but a few) utilized within avionic applications and other high temperature applications. Ideally, embodiments of such a high temperature electromagnetic coil assembly would be relatively inexpensive to produce, relatively compact and lightweight, and capable of reliable and continual operation when subjected to temperatures in excess of 260° C. It would also be desirable to provide embodiments of a method for fabricating such a high temperature electromagnetic coil assembly. Other desirable features and characteristics of the present invention will become apparent from the subsequent Detailed Description and the appended Claims, taken in conjunction with the accompanying Drawings and the foregoing Background.